‘The Greatest’ will enjoy his 70th birthday today, with admirers and well-wishers set to turn out in their thousands to celebrate his birthday in his Kentucky hometown.

He still inspires, even though his days are quiet. His wife, Lonnie, has revealed he loves watching films of his old fights, documentaries about his life and vintage Elvis movies.

Former US President Bill Clinton - in a special retrospective on Ali at 70 on Radio 5 Live on Thursday - sums up what Ali symbolises both to him, and to American society.

“He was built like a Greek god," he said. "But he just moved. He made it exciting for people and meaningful again. When he was young he was brash and always mouthing off.”

“He made it part-theatre, part-dance and all power. He was unique. And then he risked it all to oppose the Vietnam war. It could have destroyed him. But it didn't because people realised he was prepared to pay the price for his convictions. He could say, 'I put my life where my mouth was. This is the way I am prepared to live — and I'm prepared to pay whatever the consequences are for standing up for what I believe in'.

“And there was the way he dealt with his illness. It took a sackful of guts to carry that Olympic flame [in Atlanta] up that ramp, with his hand shaking, in 1996. But he did it. And it has taken a lot of courage to continue to go out, year-in, year-out. One day, somehow, it hit me. It hit me that the courage he showed as an older man struggling with Parkinson's was a different kind of — and perhaps a greater — courage than he showed as a young man.”

Those gathered in Louisville chanted “Ali, Ali...” in a lobby of the Muhammad Ali Center as four days of festivities were launched last weekend, the man himself waving from a second-floor balcony.

Then he joined 350 guests for a private party - one of five organised for him over the next two months - which doubled as a $1,000-per-person fundraiser for the Ali Center, a six-year-old cultural and education complex designed to be a legacy to his social activism, as well as a celebration of his career.

George Foreman, whose epic duel with Ali helped define both men’s careers, told The Daily Telegraph that he believes that there should be a special day to celebrate his old foe’s greatness.

“There should be Muhammad Ali Day in America, because he will go down as one of the great American heroes,” he said.

Foreman was at the dinner, as was Ali’s trainer Angelo Dundee and three American hikers, who were imprisoned in Iran. Ali, perhaps the most prominent US Muslim, had lobbied for their release.

Dundee, 91, who travelled from Clearwater, Florida, for the celebration, said he hears from Ali about once a month.

“We’re like family. We’ve always been family and we’re always going to be family. He’ll say: ‘Angie, I want to come and train. That’s what I miss the most. Being in the gym. Working up a sweat’.”

Lonnie said recently that the boxing great has mixed feelings about the landmark birthday. “He’s glad he’s here to turn 70, but he wants to be reassured he doesn’t look 70,” she said.

Born Cassius Marcellus Clay Jr. on Jan 17, 1942, Ali took up boxing at age 12. After winning Olympic gold at light-heavyweight in Rome in 1960, he went on to win the world heavyweight title against Liston. Yet while in his prime, in 1967, Ali was stripped of his heavyweight crown.

A long legal battle ended in 1971, when the US Supreme Court ruled in his favour.

"We will never know how great he could have been, because his best years were in the wilderness," boxing historian Bert Randolph Sugar, who covered every one of his fights, explained to The Daily Telegraph.

"Those were his prime years, but he became great because he stood up for what he believed in. No one will ever be able to take that away from him."

Ali retired from boxing in 1981, and devoted himself to social causes, and to fighting Parkinson’s syndrome. He remains ‘The Greatest’.

Muhammad Ali this week on tv and radio: ESPN Classic which tomorrow marks Muhammad Ali's 70th birthday with a full day of programming including his most memorable fights, interviews and documentaries.

Radio 5 Live: 8.30pm on Thursday evening: Ali at 70. A look back on the life of Muhammad Ali, including an interview with former US President Bill Clinton.